Java compiler level does not match the version of the installed Java project facet.
PROJECT_ABC123
Unknown
Faceted Project Problem (Java Version Mismatch)
source URL:
https://stackoverflow.com/questions/28995358/getting-project-facet-java-version-1-8-is-not-supported-in-eclipse-luna
I solved the problem. Go to Project Properties -> Project Facets -> Runtime -> New -> Add a tomcat server and in JRE select JRE1.8.0_XX.